Inverter



March 4, 1941. H. KLEMPERER INVERTER 3 Sheets-Sheet 1 Filed Jan. 9, 1940A. C. OUTPUT 0 3 M a i m .8 HH\ 2 l 5 l W w B .0 9 2 INVENTOR.

' HANS KLEMPERER BY My? ATTY.

FIG. 2.

TIME

March 4, 1941. KLEMPERER I 2,233,416

INVERTER Filed Jan. 9, 1940 3 Sheet's-Sheet 2 OUTPUT 12W 3 To Pemomclawn-me IMPULSES 1 FIG. 4-. Co ND ENSE R EC OUTPUT I E VOLTAGE HOLDINGAR E CONDENSER h VOLTAGE CURRENT Ta lNVENTOR.

' HANs KLEMPERER March 4; 1941. H, K RE 2,233,416

INVERTER Filed Jan. 9, 1940 3 Sheets-Sheet 3 7 76 13 OSCI LA'TORINVENTOR HANS KLEMPERER AT T Y.

Patented Mar. 4, 1941 UNITED STATES PATENT OFFICE INVERTER ApplicationJanuary 9, 1940, Serial No. 313,078

16 Claims.

This invention relates to inverters of the type in which direct currentor low frequency alternating current is converted into alternatingcurrent of a relatively higher frequency by means of controlled gas orvapor-filled electrical dis charge tubes.

An object of this invention is to increase the eiiiciency andreliability of operation of such inverters.

Another object is to increase the permissible output frequency to suchan extent that said frequency is greater than the rate at which thetubes can deionize.

Another object is to increase the power output obtainable with a givennumber of such discharge tubes.

A further object is to increase the deionization time available whereineach of such tubes may become completely deionized before a voltagetending to make them conductive is again applied thereto.

A further object is to decrease the rate at which the voltage on each ofthe discharge tubes increases at the end of the deionization time, thuseliminating any tendency for the tubes to fire prematurely.

A still further object is to fix the output frequency of the system bythe circuit constants rather than by the rate at which the tubes arefired.

The foregoing and other objects of my invention will be best understoodfrom the following description of exemplifications thereof, referencebeing had to the accompanying drawings,

wherein:

Fig. l is a diagram of one embodiment of my invention;

Fig. 2 contains a set of curves illustrating the mode of operation ofthe system as shown in Fig. 1;

Fig. 3 is a diagram of another embodiment of my invention;

Fig. 4 contains a set of curves illustrating the mode of operation ofFig. 3;

Fig. 5 is a diagram of a still further embodiment of my invention inwhich a plurality of condenser and discharge tubes are utilized; and

Fig. 6 contains curves pertaining to the operation of the arrangement asshown in Fig. 5.

In Fig. 1 direct current or relatively low frequency alternating currentis adapted to be connected to input terminals l and 2. The systemillustrated converts the input current to relatively higher frequencyalternating current which is supplied to an alternating current outputdevice primary winding H.

3. Since such a circuit usually contains both inductance and resistance,it maybe represented as in Fig. 1 diagrammatically by an inductance anda resistance. A condenser 4 is charged with current from the inputterminals 1 and 2 through an impedance 5 which is preferably aninductance. The value of this impedance is so chosen. as to maintain theproper charging rate of the condenser 8. During actual operation of thedevice, the impedance 5 tends to keep the current flowing therethroughat a substantially constant value. The charge on the condenser isadapted to be discharged into the output device 3 through a controlledignition discharge tube 6. This tube is preferably of the pool cathodetype with an igniter for initiating a cathode spot on the pool in orderto cause the tube to conduct current. Although any suitable type ofigniter may be used, it preferably is of the type described and claimedin the copending application of Percy L. Spencer, Serial No. 303,963,filed November 13, 1939, for an improvement in Are igniting devices,consisting of a conductor separated and insulated from the cathode by athin glass layer. The tube 6 is provided with an anode I connected tothe positive side of the condenser 4 in the case where the input to thecondenser is direct current. The tube 6 is likewise provided with. acathode, 8, preferably of mercury, connected to one side of the outputdevice 3. The other side of said output device is connected to thenegative side of the condenser 4. The tube 5 is provided with an igniter9, preferably of the type as described above. This igniter is adapted tobe supplied with igniting impulses from the secondary winding it of anignition transformer H having a This primary winding is supplied withperiodic peaked voltage impulses from any suitable source for ignitingthe tube 6. For example, the source may consist of a series typeinverter, such'as is illustrated in Fig. i. This inverter comprises twocontrolled ignition discharge tubes ii and M, and a pair of con densersl5 and It. Direct current to be inverted is supplied to terminals ii andit. The positive side of condenser i5 is connected directly to thepositive terminal l1 while the negative side of the condenser I6 isconnected directly to the terminal iii. The negative side of thecondenser i5 is connected to the positive side ofthe condenser IS. Thetube i3 is provided with an anode 19 connected to the positive terminalI! while the tube It is provided with a cathode 20 connected to thenegative terminal l8. The cathode 20 is preferably of thepermanentlyenergized type, as for example a thermionic filament. Thetube II also is provided with a cathode 2!, preferably 01 thepermanently-energized type, such as a thermionic filament which isconnected to one side of the primary winding l2. The other side 01' saidprimary winding is con nected to the point between the condensers II andII through an adjustable energy-consuming resistance 2|. The tube It isprovided with an anode 22 connected to one side of a primary winding 23of a transformer 24. The other side of the primary winding 23 islikewise connected through said resistance 26 to the point between thecondenser II and II. The transformer 24 is provided with ashort-circuited secondary windin'g 2I. Although the voltage impulsessupplied to the transformer 2C are not utilized in Fig. 1, they areavailable for ignition of another tube it more than one tube, such as I,is provided. The tubes I 3 and H, which are preferably of the gas orvapor-filled type, are provided with control electrodes, such as grids21 and 23, respectively. These grids are normally biased so as toprevent the tubes l3 and H from firing by means of biasing batteries 23and 30, respectively. Firing impulses are superimposed on these biasingpotentials between the anodes and cathodes of tubes l3 and H fromsecondary windings 3| and 32 of a transformer 33 which is fed withalternating current oi a suitable frequency from any suitable source ofalternating current, such as a vacuum tube oscillator 34. This vacuumtube oscillator may be of adjustable frequency. One side of thesecondary winding II is connected through the battery 29 to the grid 21,while the other side of said secondary winding Ii is connected directlyto the cathode. One side of the secondary winding 32 is connectedthrough the battery 30 to the grid 28. The other side of said secondarywinding 32 is connected directly to the cathode 20. Due to the firingimpulses supplied from the oscillator 34, the grids 21 and 23alternately render the tubes l3 and I4 conductive. As this actionoccurs, periodic peaked voltages of opposite polarity appear across thesecondary winding Ill and 25. As indicated above, the voltages appearingacross the secondary winding 25 are not utilized. The voltage impulsesappearing across the winding I0 are impressed upon the igniter 3, andthus cause the tube I to be fired upon each such igniting impulse beingsupplied thereto. 1

An auxiliary rectifier tube 35 is connected directly across the tube 6.This rectifier tube is preferably of the permanently-energized cathodetype, and therefore is provided with a cathode 35 which may be, forexample, a thermionic filament. This cathode 36 is connected to theanode I. The tube II also has an anode 31 connected directly to thecathode I.

The operation of the system illustrated in Fig. 1 maybe more clearlyunderstood by referring to the curves of Fig. 2. Along axis a Eorepresents the voltage appearing across condenser I while I representsthe current supplied from said condenser to the output device 3. On axisb, Er represents the voltage across the tubes 6 and 35. These curves donot purport to show quantita tively what happens in the systemillustrated in Fig. i, but they do represent the operationqualitatively. The charging current supplied to the condenser Igradually raises its voltage Ec until it rises to a predetermined valueat the time T1. Thereupon an igniting impulse is supplied to the igniter9, causing the tube 6 to be come conductive. The condenser 4 thendischarges through said tube I into the output device 3, delivering apulse of current I which rises to a maximum, at which time the voltageEc falls to zero. Due to the inductance of the output device 3, thecurrent I continues to flow in the same direction but decreases inmagnitude until it reaches zero at the time T2. During this period, thecondenser I charges up in the opposite direction. At T: the voltage Ecbuilt up across the condenser 4 tends to cause the current I to reverse.This reverse current cannot flow through the tube 3 inasmuch as it isarectifier. However, tube 35 which is connected in opposite polarity tothat of tube I, provides a path ior this reverse current, and thereforea pulse 0! reverse current flows during the time between T2 and T3.During this period, the voltage Es again passes through zero, and risesto a positive value at the time T3. When the current I tends to reverseat the time T3, the tube I which was extinguished at the time T1 is nolonger conductive, and therefore cannot further conduct any current.Also the polarity of the tube II is such as to oppose such flow. Thevalue to which the voltage Ec rises at the time T: depends upon thedegree to which energy has been absorbed during the time Ti-T: in theoutput device 3. The greater the degree of energy absorption, the lowerwill be this final value of EC. Actually it may be very much smallerthan the initial value to which the condenser 4 was charged, andordinarily is so low that it cannot cause the tube 6 to becomeconductive in absence of a positive firing impulse supplied to theigniter 9. Thus substantially all the energy which was not absorbed inthe output device 3 during the period Ti-T: is restored to the condenserI in the proper polarity so as to again be available to be dissipatedinto the output device I upon the next ignition of the tube 6. Due tothe conservation of this energy, the system operates very eflicientlywith a minimum of energy loss. Alter Ta, current from the inputterminals I and 2 flows to the condenser I to again charge saidcondenser to the desired voltage. Therefore, during the period Ta-T4,the voltage Ec rises gradually to the full value when the igniter Iagain fires the tube 8, and the operation described is repeated.

Between T2 and T3 the voltage across the tube 6 is only the relativelysmall voltage drop across the tube 35, and furthermore is in thenon-conducting direction on said tube I. Therefore, during the periodT2-Ta, the tube I has no tendency to pass current and has an opportunityto deionlze. At the time T3, Er across the tube I again reverses, and isimpressed upon the tube I in the conducting direction. However, aspointed out above, the value Er at the time T: is ordinarilyinsuiiiclent to cause any tendency for the tube I to fire. If at thistime the tube I has not become completely deionized and any tendency tofire exists, no harm is done because the operation, as indicated by thedotted lines in Fig. 2, occurs. If reignition of the tube I occurs atthe point T3, a succeeding pulse of current 11, as represented by thedotted lines, will be supplied to the output device 3. The voltage willfollow the dotted curve Eel, and at the end of this second currentalternation will rise to a smaller positive value than at the time Ts.This latter positive value of the voltage across the tube I being stillless than the value occurring at T: has still less tendency to cause thetube I to fire. The voltage E61 will then rise along the dotted curve toa certain value at T4 when the igniter 9 retires the tube 8. It will beseen that reignition oi the tube '6 at T3 simply results in an addedpulse of current being supplied to the load and the voltage on thecondenser 4 on the nextflrlng being somewhat reduced. Also additionalreignitions of the tube 6 following the time T: could occur withoutdisadvantageous results. As for the tube 35, no problem or deionizationtime exists therein inasmuch as that tube is intended to fire each timeits anode becomes positive.

From the analysis as given in Fig. 2, it will be seen that the frequencyof the current supplied to the output device 3 is controlled by thecircuit constants, including the value of the capacity 4 and of theinductance and resistance of the output device 3, and not by thefrequency at which the tube 8 is fired. The frequency of the outputcurrent can be made considerably. greater.

than that determined by the time during which ance with the presentinvention no longer is limited by deioniaation time of the tubes whichheretofore has constituted a serious limitation of the frequency whichsuch inverters have been able to furnish.

The effect o f varying the frequency at which the tube 6 is fired is tovary the number of high frequency current pulsations supplied per unitof time. The greater the rate at which these pulsations are supplied,the greater will be the power supplied to the output device, andconversely.

Thus by varying the frequency of the oscillator 34, the power which issupplied to the. output device 3 can be varied.

As pointed out in connection with Fig. 1, each ignition of the tube maysupply a train of current alternations to the output device. In someinstances it may be desirable to devise a system in which the productionof a train of current alternations is insured for each ignition of thetube. Such an arrangement is shown in Fig. 3. In this figure the samereference numerals are applied Where the elements are identical withthose shown in Fig. l. The tube 6 in this modification is provided withan auxiliary holding anode 38, which is connected through a resistance39 and a condenser id to the cathode ii. The condenser do is adapted tobe charged to a predetermined potential from a suitable source of directcurrent, such as a battery ll, and a current-limiting resistance 32which determines the proper charging rate for the condenser Mi.

The operation of the system shown in Fig. 3 will he better understood bya reference to Fig. i. In this figure, on axis a, EC again representsthe voltage on condenser d, while I represents the current supplied tothe output device 3. On axis b, Eh represents the voltage across thecondenser 40. As in the caseorf Fig. 1, the charging current to thecondenser 4 raises its voltage to a predetermined value, and at the timeT1 the lgniter 9 is supplied with an igniting impulse which fires thetube 6. The voltage on the condenser 4 then causes adischarge current topass through the tube 6 into the output device 3. At the time T1likewise the voltage En has risen to a predetermined value, due to thecharging current flowing to the condenser 40 from the battery 4|. Whensequence of operations is repeated.

the tube 5 is ignited, a discharge current flows from the condenser 40through the resistance 89 and anode 38 to an are spot established on thecathode 8. The'resistance 39' is of a value to give a relatively longtime constant to the discharge circuit of condenser 40, so that thevoltage Eh falls off, as shown between T1 and T2 in Fig. 4. Throughoutthis time a holding arc is maintained between the cathode 8 and theanode 38, so that a discharge may p ss to the anode 1 each time itbecomes positive throughout this period. Therefore the currentpulsations from the discharge circuit of condenser 4 which tend to fiowin one direction pass through the tube 6 from the anode I. The currentwhich tends to flow in the opposite direction passes through the tube 35from the anode 31. As a result, a train of current a1- ternations I ofdecreasing amplitude is supplied to the output device 3, and the voltageEc across the condenser 4 likewise is alternated with decreasingamplitude. At T2 the voltage and consequently the current'fiowing fromthe anode 38 falls to such a value that it is incapable of maintainingan arc to the cathode 8, whereupon said are is extinguished. If atthistime current is still flowing from the anode I, such current willcontainue to flow until it has fallen substantially to zero, whereuponthe tube 35 will cause an additional pulse of current to flow in theopposite direction, and then cease, as explained in connection withFigs. 1 and 2. The voltage EC on the condenser 4 at the time of theextinction of the tube 35 again has a positive value which representsany energy which has not been absorbed in the output circuit. However,due to the fact that the output circuit has been supplied with a trainof current alternations, the energy absorption is considerable, andtherefore the final value of E0 is very low, entirely eliminating anyfurther tendency for the tube 6 to fire. Here again an additionalignition of the tube 6 does no harm, merely resulting in an additionalalternation of current supplied to the output circuit. Voltage Ecagainrises to its maximum value, due to the charging current flowing thereto,and at the time T; the igniter 9 again ignites the tube 5 and the Duringthe time Tz-Ta, the condenser 40 likewise recharges from the battery 43,and the voltage En rises, as indicated in Fig. 4, to its maximum valueso as to be available for establishing a holding are as explained above.

In the case of Figs. 3 and 4, the frequency again is determined by thecircuit constants rather than by the frequency at which the tube '6 isignited. Here again the output frequency can be much greater than thespeed with which the tube 6 can be deionized, so that the system cansupply high frequency current with extreme reliability.

As mentioned in connection with Fig. 1, additional ignition tubes may beutilized for supplying current pulsations to the output. As a matter 'offact, any number of such tubes together with associated condensers maybe combined in a single system whereby the power output obtainable ismultiplied. Such an arrangement is shown, for example, in Fig. 5. Inthis figure direct current or relatively low frequency alternatingcurrent is adapted to be connected to the input terminals 43 and 44 andalternating current supplied to an output device 45 similar to theoutput device 3 of Fig. 1. A plurality of 'condensers, for example threein number, 46, 61

(iii

between the input terminal 44 said condensers.

One side of each 0! said condensers, which may be the positive side inthe case of a direct current supply, are connected to the input terminal48. The condensers 48, 41 and 48 are adapted to bedischarged into theoutput device through controlled ignition discharge tubes 52, 53 and 54.These tubes are preferably of the same type as tube 6 described inconnection with the previous figures. These tubes are provided with poolcathodes 55, 56 and 51 connected respectively to the negative sides ofthe condensers 46, 41 and 48. These controlled ignition tubes likewiseare provided with anodes 58, 58 and 60, respectively, which areconnected together through the output device 45 to the terminal 43. Thetubes 52, 53 and 54 are likewise provided with igniters 6|, 82 and 63,respectively. These igniters are adapted to be supplied with ignitingimpulses from secondary windings 84, and 55 of ignition transformers 81,88 and 69, respectively, whose primary windings 10, H and I2 are adaptedto be supplied in sequence with igniting impulses from any suitablesource. As illustrated in Fig. 5, these igniting impulses are suppliedto said primary windings from a supply transformer 16 having secondarywindings I3, 14 and I5 connected in star. The outer ends of saidsecondary windings are connected in series with the primary windings 18,II and 12 whose outer ends are grounded. Said supply transformersecondary is likewise provided with a grounded neutral [9. Thetransformer I5 is provided with a primary winding ll connected forexample in delta and supplied with a three-phase voltage from a suitablethree-phase oscillator 18. This oscillatoris preferably of the typewhich supplies peaked voltage waves to each of the three phases of thetransformer. In this way the secondary windings 64, B5 and 56 aresupplied in sequence with peaked igniting bu pulses which cause thetubes 52, 53 and 54 to be ignited in sequence. These tubes areordinarily constituted so that a tendency for an arc spot to form. ontheir associated cathodes occurs only when the ignlter is made positivewith respect to its associated cathode, and therefore these tu willordinarily fire only on the positive voltage peaks supplied by thetransformer 16,

In order to provide a path for the negative pulses of current whichcannot flow through the tubes 52, 53 and 54, as explained in connectionwith the previous embodiments, an auxiliary dls charge tube Bil isprovided. This tube contains a cathode of the permanently-energized typewhich may be, for example, a pool of mercury to which a holding arc ismaintained by means of auxiliary holding anodes. Thus tube con tainssuch a pool cathode 8i and a pair of ou iliary holding anodes lit. Theseanodes are c nected to opposite sides of the secondary wind ing 83 of aholding transformer 84 whose primary winding 85 is adapted to besupplied from a sult able source of alternating current. The secoi arywinding 83 is provided with a center tap i. connected through aninductance B1 to the ode 8!. An are spot is established on the cathodeBl by any suitable igniting means which may be,

for example, an igniter of the type as indicated in connection withtubes 52, 53 and 54. Thereupon current flows alternately from the twoanodes 82 to the are spot on the cathode. These currents overlap, due tothe inductance 81, so that the cathode spot is permanently maintained.The constants of the transformer 84 and the associated circuit are sochosen that a reasonable value of current flows from the anodes 82.

The cathode 8| is connected directly to the common lead extending to theanodes of the tubes 52, 58 and 54. The tube 80 ls'likewise provided withthree anodes 88, 88 and 80 connected respectively to the cathodes 55, 56and 51.

When the system described above is energized, the condensers 48, 41 and48 each acquire a charge from the input terminals 43 and 44. One of thetubes, for example 52, is ignited by an ignition impulse being suppliedto the igniter Bl. Thereupon the condenser 46 discharges through saidtube 52 into the output device 45. When the discharge current flowingfrom the condenser 48 tends to reverse, as explained in connection withthe previous embodiments, such reverse current can flow from the anode88 to its associated cathode 8|. Thus the operation of the condenser 42,the tube 52, and the anode 88 of tube B0 opcrates exactly as explainedin connection with the operation of the single pair of tubes of Figs. 1and 3. Following the sequence of operations established by igniting thetube 52, the tubes 53 and 54 are ignited in sequence. Each such ignitionproduces a similar sequence of operations, each resulting in furnishingthe output device 45 with one or more alternations of high frequencycurrent. As indicated in Fig. 6, the output current supplied by ignitingthe tubes 52, 53 1 and 54 are combined in the output device 45. Thus,for example, Ia represents the current supplied irom condenser 46 andtube 52; I1), the current from condenser '31 and tube 53; and I0, thecurrent from condenser 48 and tube 5t. Each of these currents follow oneanother in sequence in the output device t5, and therefore although eachoi? the tubes 5?, 53 and M fired at a certain frequency, the number oicurrent pulsa- 'tions supplied to the output device t? is the sum oi thecurrent pulsations supplied from these tubes.

.-ls explained in connection with the previous dhnents, the irequency oithe output cur is det by the rate at which the tubes are o the whichupplied to the out it s determined by the n mber oi current uippliedunit or me. liiy uti y of such tubes, as indicated in l -'.s..ter numberor" such cur c t oulsu is unit oi? time can be supplied to output andtherefore this embodiment presents system. course is to be understoorilthat this in to the particular do ry equivalents will so Milled in theart. In the where alteruatins c1. nt impressed upon input terminals, beunderstood tl'lat system .i one] oh the positive half of r..:ot cycle. osystems may hi both halves oi su 'esscd alterna current Wave. Also others or tubes d control devices could be no. red. Various othermodifications and ideas as to the utilization of the principlesenunciated herein will suggest themselves to those skilled in the art.pended claims be given a broad interpretation commensurate with thescope of the invention within this art.

What is claimed is z 1. An inverter comprising condenser means,

d. Ii

"lined by the circuit constants rather It is accordingly desired thatthe apaugemetot for increasing the power output ignition rectifyingspace discharge means for 2,283,416 means for charging said condensermeans, an

- lations in said discharge to a predetermined number, and means forinitiating the'discharge operation of said space discharge means at apredetermined frequency.

2. An inverter comprising condenser means, means for charging saidcondenser means, an alternating current output circuit, space dischargemeans for discharging said condenser means into said output circuit byan oscillating discharge whose frequency is determined by the condensermeans and its associated discharge circuit and for limiting the numberof current oscillations in said discharge to a predetermined numher, andmeans for. initiating the discharge operation of said space dischargemeans at a predetermined frequency which'is less than said oscil latingfrequency.

- 3. An inverter comprising condenser means, means for charging saidcondenser means, an alternating current output circuit, ionizable gas orvapor-filled space discharge means for discharging said condenser meansinto said output circuit by an oscillating discharge whose frequency isdetermined by the condenser means and its associated discharge circuitand for limit-' ing the number of current oscillations in said dischargeto a predetermined number, said oscillating frequency being greater thanthat determined by the deionization time of said space discharge means,and means for initiating the discharge operation oi said space dischargemeans at a predetermined irequency which is less than said oscillatingfrequency.

4. An inverter comprising condenser means, means for charging saidcondenser means, an alternating current output circuit, controlledignition rectifying space discharge means for discharging said condensermeans into said output circuit by an oscillating discharge, rectifyingmeans of opposite polarity to said space discharge means connected toprovide a path for the negative part of said oscillating discharge, andmeans for igniting said space discharge means at a predeterminedfrequency.

5. An inverter comprising condenser means, means for charging saidcondenser means, an alternating current output circuit, controlleddischarging said condensermeans into said output circuit by anoscillating discharge, rectifying means of opposite polarity to saidspace discharge means connected across said space discharge means, andmeans for igniting said space discharge means at a predeterminedfrequency.

6. An inverter comprising condenser means,

means for charging said condenser means, an

alternating current output circuit, pool cathode type rectifying spacedischarge means for discharging said condenser means into said outputcircuit by an oscillating discharge, rectifying means of oppositepolarity to said space discharge means connected across said spacedischarge means, and means for initiating arc spots on said cathode at apredetermined frequency.

7. An inverter comprising condenser means, means for charging saidcondenser means, an alternating current output circuit, a discharge tubehaving a pool type arcing cathode and an anode connected in series withsaid condenser means and said output circuit, a rectifying tube having apermanently-energized type of cathode connected to said anode, and ananode connected to said pool type cathode, and means for initiating arcspots on said pool type cathode at a predetermined frequency.

8. An inverter comprising condenser means, means for charging saidcondenser means, an alternating current output circuit, space dischargemeans for discharging said condenser means into said output circuit byan oscillating discharge, said discharge means comprising a dischargetube having a pool type arcing cathode and an anode connected in serieswith said condenser means and said output circuit, rectifying means ofopposite polarity to said space discharge means connected across saidspace discharge means, means for establishing a holding arc to said pooltype cathode for a plurality of the periods of said oscillatingdischarge, and means for initiating arc spots on said pool type cathodeat a predetermined frequency.

9. An inverter comprising condenser means, I

means for. charging said condenser means, an alternating current outputcircuit, controlled ignition rectifying space discharge means fordischarging said condenser means into said output circuit by anoscillating discharge, rectifying means of opposite polarity to saidspace discharge means connected across said space discharge means, andmeans for igniting said space discharge means at a predeterminedfrequency and for maintaining said space discharge means ignited for aplurality of the periods of said oscillating discharge.

10. An inverter comprising a plurality of condenser, means, means forcharging said condenser means, an alternating current output circuit, a

plurality of space discharge means for discharg.

ing said condenser means in sequence into said output circuit by anoscillating discharge whose frequency is determined by each condensermeans and its associated discharge circuit and for limiting the numberof current oscillations in said discharge to a predetermined number, andmeans for initiating the discharge operation of each of said spacedischarge means in sequence at a predetermined frequency.

11. An inverter comprising a plurality of con denser means, means forcharging said condenser means, an alternating current output circuit, aplurality oi space discharge means for discharging said condenser meansin sequence into said output circuit by an oscillating discharge, andmeans for initiating the discharge operation of each of said spacedischarge means in sequence at a predetermined frequency whichis lessthan said oscillating frequency.

12. An inverter comprising a plurality of com denser means, means forcharging said condenser means, an alternating current output circuit, aplurality of ionizable gas or vapor-filled space discharge means fordischarging said condenser means into said output circuit by anoscillating discharge whose frequency is determined by the condensermeans. and its associated discharge circuit and for limiting the numberof current oscillations in said discharge to a predetermined number,said oscillating frequency being greater than that determined by thedeionization time of said space discharge means, and means forinitiating the discharge operation of each of said space discharge meansin sequence at a predetermined frequency which is less than saidoscillating frequency.

13. An inverter comprising a plurality of condenser means, means forcharging said condenser means, an alternating current output circuit, aplurality of controlled ignition rectifying space discharge means fordischarging said condenser means into said output circuit by anoscillating discharge, rectifying means 01 opposite polarity to saidspace discharge means connected across each of said space dischargemeans, and means for igniting each of said space discharge means insequence at a predetermined frequency.

14. An inverter comprising a plurality of condenser means, means forcharging said condenser means, an alternating current output circuit, aplurality of pool cathode type rectifying space discharge means fordischarging said condenser means into said output circuit by anoscillating discharge, rectifying means of opposite polarity to saidspace discharge means connected across each of said space dischargemeans, and means for initiating arc spots on each oi said pool typecathodes at a predetermined frequency.

15. An inverter comprising condenser means, means for charging saidcondenser means, an alternating current output circuit, a dischargetubehaving a cathode and an anode connected in series with said condensermeans and said output circuit, a rectifying tube having apermanentlyenergized type of cathode connected to said anode, and ananode connected to said iirstnamed cathode, and means for firing saiddischarge tube at a predetermined frequency.

16. An inverter comprising a plurality of condenser means, means iorcharging said condenser means, an alternating current output circuit, aplurality of discharge tubes each having a cathode an an anode connectedin series with each of said condenser means and said output circuit, arectifying tube having a permanently-energized type of cathode connectedto all of said anodes, and a plurality of anodes connected to each ofsaid first-named cathodes, and means for firing said discharge tubes insequence at a predetermined frequency.

HANS KLEMPERER.

